Active styluses are known in the art for use with a touch enabled computing device. An active stylus interacts with a touch-screen of the device based on emitting a signal at or near its writing tip. The signal emitted is generated with a signal generator housed in the stylus. The signal generator may generate a position signal and may also generate modulation including information such as pressure applied on the writing tip and stylus identification.
The touch-screen includes a Flat Panel Display (FPD) integrated with a digitizer sensor. Integration may be based on the digitizer sensor overlaid on the FPD, integrated on a protective glass layer of the FPD (on-cell technology) or integrated as part of the FPD (in-cell technology). The digitizer sensor typically includes a matrix of electrode junctions arranged in rows and columns.
The signal emitted by the active stylus is picked up by the digitizer sensor when electrostatic coupling is established between the writing tip and a portion of the matrix of electrode junctions. The electrostatic coupling is a result of proximity of the writing tip to the digitizer sensor. Positions of the writing tip over the screen are correlated with virtual information portrayed on the touch-screen. Digitizer sensors that track signals emitted by the stylus also typically track input provided with a finger or conductive object. A mutual capacitive sensor is one type of digitizer sensor that is integrated with FPD to form a touch-screen.